There are already known various arrangements for detecting penetration of humans into and/or their movement in a controlled region. Such detecting arrangements are being used, for example, to defend a perimeter of an installation, to monitor movement of personnel within an installation, to detect the presence of people on premises or the like. Detecting or sensing equipment of different types has been used, more or less successfully, for the above and similar detecting purposes. So, for instance, U.S. Pat. No. 4,263,585 discloses an intrusion detection system in which a multi-segment mirror focuses thermal radiation emanating from a moving person onto a thermopile detector in such a manner that each mirror segment separately directs the radiation in succession to detector elements, whereby the direction of movement of such a person can be determined. Another control device responsive to infrared radiation is disclosed in U.S. Pat. No. 4,346,427, wherein an infrared sensor is being used to detect any movement of a person into or within the region under surveillance. The output signal of this sensor is utilized for controlling the operation of lights, air conditioning or the like for the affected region. A control device of this type is also disclosed in the published international patent application No. PCT/US81/01769 (International Publication No. WO 82/02270). Moreover, a passive infrared occupancy detector of a similar type has been developed by Tishman Research Co. and United Technologies Corporation and is commercially available under the designation Infracon Model 628.
As advantageous as the above devices may be for the purposes for which they have been developed, they are not well suited for determining the number of people passing through the region under surveillance, such as an elevator doorway, and the direction of passage of such people through the surveillance region. Yet, in some instances, it would be desirable to possess this information so as to be able to use it for various purposes, such as for determining the number of people present in an elevator in order to estimate the elevator load, for determining the number of people entering and leaving an elevator at any of the various floors of a building to determine the traffic flow pattern in the building for use in elevator dispatching, or the like. However, until recently, no attempts have been made to utilize any such known detecting equipment of the above kind for controlling the operation of elevators, in spite of the fact that the previously existing elevator dispatching techniques left much to be desired as far as their effectiveness and responsiveness were concerned, since elevator control systems employing such known dispatching techniques were being operated solely on the basis of floor calls, albeit possibly taking into consideration some recurring traffic patterns, for instance, those ordinarily repeating themselves in the course of the day.
In any event, however, elevators have heretofore usually been dispatched to the various floors without any real-time information as to the actual traffic flow. More particularly, no attempts have been made in the performance of such preexisting elevator dispatching techniques to use or even to gather information concerning the number of people waiting at a landing, be it because it was not recognized that this information, while presenting less than a complete picture of the traffic flow to occur in that the destination floors of the people waiting for an elevator to arrive would not be known, could nevertheless be used in controlling the operation of the elevator in a considerably more economical manner than that possible before, without unduly burdening the people waiting for the elevator to arrive or those already in the elevator, or because it was felt that it would be impossible to reliably collect this information or that the cost of gathering this information would outweigh any benefits derived therefrom, or for other reasons. It was not until quite recently that it was recognized that the above information could indeed be used to advantage in controlling the operation of elevators, and that attempts have been made to develop approaches to the gathering and use of such information. So, for instance, it was proposed to utilize passive infrared sensors for such applications. Yet, the heretofore proposed approaches left much to be desired, especially as far as the accuracy or veracity of the information gathered by such detecting equipment was concerned.
On the other hand, various attempts have already been made, mainly for safety reasons, to develop techniques for measuring or estimating the elevator load, such as weight-measuring sensors mounted on the elevator. However, equipment of this type is sensitive only to the total weight of the elevator occupants and not to their number. In other words, this equipment is not capable of distinguishing between the presence in the elevator of, say, on the one hand, one elevator user who is rather heavy, and on the other hand, two or three elevator users who are individually much lighter. Thus, this equipment does not provide reliable information about the actual number of elevator occupants or about the actual number of people entering or leaving the elevator at the particular floors. To avoid this inadequacy, it was proposed to provide doubled light barriers strategically positioned across the elevator doorway, the idea being that a person entering the elevator will interrupt one light beam first and the other light beam second, while a person leaving the elevator will interrupt the other light beam first and the one light beam second. However, experience with this approach has shown that the obtained results are very unreliable since they can be rather easily adversely affected by two people simultaneously entering and/or leaving the elevator, by hand or leg movements of the person entering or leaving the elevator, by obscuration caused by a hand or an arm of a person holding the elevator door, or the like.
Accordingly, it is a general object of the present invention to avoid the disadvantages of the prior art.
More particularly, it is an object of the present invention to provide an arrangement for detecting passage of living beings through a surveillance region, which arrangement does not possess the disadvantages of the known arrangements of this kind.
It is yet another object of the present invention to develop the arrangement of the above type in such a manner as to be able to generate reliable information as to the number of people present in an elevator or in any other enclosed space, such as an elevator landing, at any given time.
Still another object of the present invention is to design the above arrangement in such a manner as to be able to accurately individually record the entry of people into and their exit from the enclosed space even if such people enter and/or leave the enclosed space simultaneously.
A concomitant object of the present invention is so to construct the above arrangement as to be relatively simple in construction, inexpensive to manufacture, easy to install and use, and reliable in operation nevertheless.